During the epidemics of the mediaeval period, doctors in Byzantium and Italy developed the “Alipta muscata” as a preventive medicine against epidemics. When treating the “black death” doctors constantly used it for self-medication. The main ingredient of “Alipta muscata” was the oleoresin labdanum of Cistus creticus L. [1]. While the “black death” is mostly interpreted as Yersinia pestis, there is also an alternative interpretation as a viral haemorrhagic fever [2]. We tested several extracts and fractions of labdanum on their activity against the dengue virus (DENV-2 strain 00st-22A) in in vitro cultures on Vero cells (96-well-plates, 5 days). This haemorrhagic fever affects up to 500 million patients annually with no chemotherapeutic agent available and causes 20.000 deaths. Preliminary experiments with a labdanum full extract did not yield measureable results due to cytotoxic effects against Vero cells. In all following experiments, cell viability was constantly checked using the MTT-test. Fractionation of the dichloromethane raw-extract by liquid-liquid-extraction and column-chromatography on silica-gel (gradient elution with Hexane, EtOAc, CHCl3, MeOH) succeeded in separating the anti-viral activity of labdanum from its cytotoxic effect. In the most active fraction GS5 at 30 µg/ml, the dengue virus proliferation was 100% suppressed and cell viability over 90%. Structural elucidation of major constituents of GS5 is currently ongoing. Claims concerning the antiviral activity of above ground parts of C. creticus have been made previously, but these generally ascribe this activity to hot water soluble polyphenols and propose an unspecific tanning effect of the viral surface proteins as the mechanism of action [3]. We describe an antiviral activity of a dichloromethane extract of labdanum against a virulent haemorrhagic fever like dengue for the first time.
[1] Husemann T. Archiv der Pharmacie. 1889;27:1075 – 1132
[2] Duncan CJ, Scott S. Postgrad Med J. 2005;81:315 – 20
[3] Ehrhardt C et al. Antiviral Res. 2007;76:38 – 47
